1. Field of the Invention
This invention relates to a method for decomposition of a bond magnet, which is superior in dimensional accuracy and processing and is widely applied to industrial materials.
2. Related Art of the Invention
A bond magnet is a magnet molded by blending hard magnetic powder-like material with binder such as plastics and rubber. Every type of hard magnetic materials is generally hard and fragile in quality. Process for manufacturing the materials are generally performed finally by finish machining in order to realize a fixed size by molding, sintering and heat-treating. As a result, high processing cost is unavoidable for use requiring strict dimensional allowance, and thus significant increases in product cost may be caused. Further, complexly-shaped or thin materials are difficult to produce. A bond magnet is manufactured for the purpose of resolving these disadvantages in processing. The bond magnet is characterized in that it has high dimensional accuracy in processing, a complexly-shaped or thin material, or the like, is easy to process without fractured and chipped, and furthermore it is light in weight. Since the bond magnet contains 2-15 wt % (25-50 vol %) of non-magnetic material binder, magnetic characteristics are inferior to a casing magnet or sintered magnet. However, since powerful magnetic powder such as rare-earth magnet could be obtained, characteristics of a magnet are rapidly improved and such a powerful magnet is used widely.
On the other hand, since a bond magnet is manufactured as a blend of binder and magnetic powder-like material, decomposition and reuse for resources of the used bond magnet or bond magnet with inferior quality are difficult. Especially, in the case where the binder is thermosetting resin, insoluble and non-melting three-dimensional solid structures are generally produced by curing reaction. Therefore, cured resin was difficult to decompose and was not proper for recycling and reuse.
Considering the increasing serious problems of waste and effective use of resources, the development of processing technology for reducing the volume of waste, waste treatment technology for reuse, or the like, for the used and inferior bond magnet is urgently required. Especially, the bond magnet is mainly made of metal, metallic oxide or the like, and metals or the like are more expensive materials than resinous binder materials. Consequently, the fact that reclamation and reuse of such expensive materials cannot be performed, is a large problem. Moreover, in case of a magnet made of rare earth metals such as cobalt, neodymium or the like, or other materials, the problems are still more serious. A bond magnet, which is manufactured by using thermosetting resin such as epoxy resin or the like as a binder, is completely difficult to decompose. A method for decomposition of any type of bond magnet in order to isolate metals such as rare earth metals or the like from the bond magnet is required.
Any conventional configuration or method for decomposition of a bond magnet cannot be sufficiently applied for reuse or recycle as resources at present.
An object of the present invention is to provide an easy and simple method for decomposition of a bond magnet.
A method of the present invention for decomposition and treatment of a bond magnet, comprises:
a decomposition process for making a bond magnet which is made by blending magnetic powder-like material with binder and being molded, contact with decomposition material which can decompose said binder, within a decomposition vessel;
a removing process for removing oxygen in the decomposition vessel; and
a heating process for heating the decomposition vessel in temperatures ranging from 250xc2x0 C. to just under a critical temperature.
A process for removal of oxygen is preferably to exhaust the gas in the decomposition vessel after replacing the gas in the decomposition liquid with nitrogen gas by supplying nitrogen gas, and then to reduce the pressure in the decomposition vessel.
A method of the present invention for decomposition and treatment of a bond magnet, comprises:
a decomposition process for making a bond magnet which is made by blending magnetic powder-like material with binder and being molded, contact with decomposition material within a decomposition vessel, said decomposition material containing at least one solvent selected from the group including tetralin, biphenyl, naphthalene, methylnaphthalene, 1,4-hydroxynaphthalene, naphthol, 1,4-naphthoquinone, pitch, creosote oil, methylisobutyl ketone, isophorone, 2-hexanone, 2-heptanone, 4-heptanone, diisobutylketone, acetonylacetone, phorone, cyclohexanone, methylcyclohexanone and acetophenone; and
a heating process for heating the decomposition vessel in temperatures ranging from 250xc2x0 C. to just under a critical temperature.
In the method for decomposition of the present invention, a liquid for decomposition is preferable to contain antioxidant or reducing agent.
Antioxidant or reducing agent is preferably at least a compound selected from the group consisting of hydroquinone, methoquinone, benzoquinone, naphthoquinone, butylcatechol, butylhydroquinone, sodium hyposulphite, soduim thiosulfate and ascorbic acid.
In the method for decomposition of the present invention, a preferable example of the bond magnet, which is molded by blending magnetic powder-like material with binder, is the bond magnet consisting of a rare-earth magnet containing a rare earth element as a magnet material.